Duration of igneous activity in the Sesia Magmatic System and implications for high-temperature metamorphism in the Ivrea-Verbano deep crust
Duration of igneous activity in the Sesia Magmatic System and implications for high-temperature metamorphism in the Ivrea-Verbano deep crust
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DOI：
10.1016/j.lithos.2014.07.020
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发表时间：
2014-10-01
期刊：
影响因子：
3.5
通讯作者：
Guenes, Zekerias
中科院分区：
文献类型：
--
作者：
Kloetzli, Urs S.;Sinigoi, Silvano;Guenes, Zekerias
意大利北方的伊夫雷亚-韦尔巴诺带和塞列代拉吉构成了亚得里亚海大陆地壳的一个几乎完整的部分，这些大陆地壳在不同的水平上被二叠纪-石炭纪时代的同时代岩浆侵入，统称为“塞西亚岩浆系统”。在剖面的最深处，可以研究Ivrea-Verbano带岩浆底侵作用和麻粒岩相变质作用之间的关系。我们提出了新的锆石U-Pb年龄数据，显着扩展了该地区的岩浆活动记录，并表明岩浆脉冲开始侵入中地壳和深地壳不晚于314 Ma，对应于推断的区域麻粒岩相变质作用的年龄，并早于20多万年。有据可查的主要岩浆脉动发生在大约292至282 Ma之间。在Ivrea-Verbano带的深地壳麻粒岩相副片麻岩中观察到的年龄信息的差距从316 +/- 3 Ma到276 +/- 4 Ma，与密切相关的镁铁质超镁铁质岩床中的火成岩和重置锆石之间的差距从大约314到283 Ma重叠。然而，锆石年龄显示，侵入活动在中地壳和上地壳在这个时间间隔。我们推断，地壳深部副片麻岩中锆石饱和度以上温度的长期维持可以解释这些岩石中锆石年龄的差距。从这个角度来看，在高等级火山岩中的地质年代学记录中的空白可能不一定意味着没有事件，而是可能记录了热峰的发生和持续时间。(C)2014爱思唯尔有限公司版权所有。
The Ivrea-Verbano Zone and Serie dei Laghi of northern Italy constitute a virtually complete section of the Adriatic continental crust, which was intruded at different levels by coeval magmas of Permo-Carboniferous age, collectively referred to as the "Sesia Magmatic System". At the deepest levels of the section, the relationship between magmatic underplating and granulite-facies metamorphism in the Ivrea-Verbano Zone may be studied. We present new zircon U-Pb age data, which significantly extend the record of igneous activity in this terrane, and which demonstrate that igneous pulses began intruding the deep and middle crust no later than 314 Ma, an age corresponding to that inferred for regional granulite-facies metamorphism and predating by more than 20 m.y. the well-documented, main magmatic pulse at about 292 to 282 Ma. A gap in age information from 316 +/- 3 Ma to 276 +/- 4 Ma, observed in the deep-crustal granulite-facies paragneiss of the Ivrea-Verbano Zone overlaps a gap from circa 314 to 283 Ma between igneous and reset zircons in a closely associated maficultramafic sill. However, zircon ages demonstrate intrusive activity in the middle and upper crust during this time gap. We infer that prolonged maintenance of temperatures above zircon saturation in the deep-crustal paragneiss could explain the gap in zircon ages in those rocks. Viewed in this light, a gap in a geochronological record within high-grade terranes might not necessarily mean an absence of events, but instead may record the occurrence and duration of a thermal peak. (C) 2014 Elsevier B.V. All rights reserved.